The medical practice utilizes a number of procedures and indicators to assess a patient's condition. Some medical diagnosis and treatment practices require invasive procedures for accurate treatment. For instance, a common invasive procedure involves the measurement of blood glucose, wherein an invasive blood glucose measurement device can be used to prick a patient's finger, collect a blood sample, and measure the blood glucose level externally. Other types of medical diagnosis and treatments may be performed non-invasively. For example, pulse oximetry is a non-invasive method for monitoring a patient's O2 saturation. To measure pulse oximetry, a photodetector sensor is placed on a thin part of the patient's body, usually a fingertip or earlobe, or in the case of an infant, across a foot. Light is passed through the patient to a photodetector. An analysis of the light can be used to determine the patient's oxygen saturation. There is a growing desire within the medical community to move away from invasive procedures and develop instruments to assess and monitor functions continuously and in real time in a non-invasive and non-obtrusive way. Non-invasive monitors reduce the need for long hospitalization periods. Non-invasive monitors also reduce healthcare costs and improve patient comfort and safety. In recent years, electrocardiograms, intermittent blood pressure monitors and pulse oximeters have been used to non-invasively monitor patients' blood pressure and/or oxygen levels. Unfortunately, these devices still provide an incomplete picture of a patient's health status.